We are investigating the possibility of cutting serial sections of plastic embedded biological material that are thinner that has previously been possible. We have obtained several knives from Diatom USA and have borrowed an Ultra-S Microtome from Leica, Inc. to see what the practical limitations are on section thickness. By using an isolation room to minimize air currents, a vibration damping table to minimize this perturbation, and specimens embedded of a variety of plastics, we have been able to obtain sections that are less than 11nm thick. These cut with reasonable uniformity (+ 10%) and may be obtained in large numbers (>100). By using methanolic uranyl acetate to stain them and a small objective aperture in a conventional electron microscope operating at 60kv we have obtained good image contrast. We are now working to make this technology effective for immunolocalization as well as 3-D reconstruction.